Machines, often referred to as "chipper-shredders," have been in wide use for years for comminuting lawn and yard refuse. Owners of residential and commercial property use such machines to mulch grass clippings, small twigs and branches, leaves and the like. In the past, it had been common practice to place the comminuted refuse into bags and dispose of the bags and refuse in a landfill.
More recently, municipalities are becoming more concerned about the cost of procuring landfill space. A growing number of such municipalities prohibit many types of lawn refuse from being placed into a landfill. Consequently, chipper-shredder machines are increasing importance since they reduce lawn refuse to small particle and "piece" sizes entirely suitable for use as garden, lawn and tree mulch. Chipper-shredder machines play an important part in returning valuable natural organic material, pulverized lawn refuse, to the soil.
There are number of manufacturers of such chipper-shredder machines and the patent literature illustrates several different machine configurations. Examples of such machines are shown in U.S. Pat Nos. 5,156,345 (Baker); 5,102,056 (Ober); 4,824,034 (Baker); 4,544,104 (Carlsson); 3,817,462 (Hamlin) and others. While such machines have been generally satisfactory for their intended purpose, they are characterized by certain disadvantages.
Many chipper-shredder machines include the capability to attach a vacuum hose to the machine and clean up lawn refuse "fines" by vacuum. One disadvantage of certain known chipper-shredder machines involves the vacuum hose arrangement. The configurations shown in U.S. Pat. Nos. 5,018,672 (Peck); 4,875,630 (Carlson) and 3,712,353 (Ferry) are typical in that all use a side-mounted vacuum hose.
Such side-mounting arrangements are thought to have little pivoting capability. And in any event, it is very clear that a substantial length of hose is required just to position the vacuum mouth to the side of the machine opposite the mounting opening. Further, the hose used for such purpose is often specially selected for such applications and is relatively expensive. Some hoses require tools for attachment and removal.
Chipper-shredders are usually equipped with "free-swinging" comminuting "hammers" or blades attached to a grinding rotor. Often, the blades are Y-shaped and the two arms of the "Y" are bent slightly in opposite directions away from the plane of the blade body. Examples of blade configurations of this general type are shown in U.S. Pat. Nos. 1,211,566 (Fortney) and 1,975,406 (Reschke). A disadvantage of this blade type is that twigs and small branches tend to become wedged between the blades and carried around with the grinding rotor rather than being chopped.
Still another disadvantage of known chipper-shredders arises from the inclusion of a branch-receiving chute or tube. Small branches are thrust into the tube to be ground up by the rotor. Examples of such chutes are shown in the above-noted Ober and Baker '034 patents. Often, the tube is simply left open when not in use. If open, air flows down the tube while the vacuum hose is being used and reduces the vacuum hose "cleanup" capability of the machine. If the tube is closed when not in use, it is typical to employ a custom-fabricated closure for the purpose. One manufacturer uses a permanently-attached, spring-biased swinging plate.
Another disadvantage of known chipper-shredders is their tendency to "walk" or "dance" when in use. This annoying characteristic occurs when the machine rests on a hard surface, e.g., a concrete or asphalt driveway, and is especially typical of chipper-shredders powered by internal combustion engines and having a "cantilevered" drive shaft, i.e., a drive shaft with no outboard support bearing. Such engines inherently exhibit more vibration than electric motors and cantilevered drive shafts tend to whip slightly due to the almost inevitable imbalance in load.
Still another disadvantage of known chipper-shredders is that their prime mover, e.g., a gasoline engine or an electric drive motor, is mounted in such a way that the machine is very difficult to move from location to location. U.S. Pat. No. 5,085,376 (Litchenburg) shows a machine in which the gasoline engine is mounted well away from the wheel axle. Tipping or lifting the machine is thereby made unnecessarily difficult.
Yet another disadvantage of known chipper-shredders involves the manner of mounting the chipper knives which are preferably seated in some sort of pocket to help reduce the stress on the knife-securing bolts. In certain known products, the pocket is formed in the chipper plate by a milling operation which involves removing metal from the plate. Another known way to form a pocket is to grind it. And yet another known chipper-shredder does not use a pocket at all but, rather, welds a back-up bar onto the chipper plate to support the knife. These operations add significantly to the cost of manufacture.
An improved chipper-shredder which incorporates features addressing the above and other disadvantages would be an important advance in the art.